1. Field of the Invention
The present invention relates to backlight modules, more particularly, to frames for use in backlight modules of liquid crystal display device.
2. Description of the Related Art
Nowadays, as light weight and thin body of personal computers, notebook computers and communications equipment are required, and the need of liquid crystal display unit rises as well. A typical liquid crystal display unit mainly comprises a chassis, a liquid crystal display panel and a backlight module. In view of the liquid crystal display panel emitting no light, the backlight module is necessary for the liquid crystal display panel to provide enough light; therefore, designs of backlight module become more and more important.
Referring to FIG. 1, it shows a cross-sectional view illustrating a liquid crystal display device of U.S. Pat. No. 5,966,191, wherein a backlight module comprising a sheet set 2, a light guiding plate 3 and a light source 4 disposed on at least one of terminals of the light guiding plate 3. The sheet set 2 which has a top and an edge comprises a protecting sheet 21, a prism sheet 22, a diffusing sheet 23, and/or a reflecting sheet 24. The whole backlight module is fixed by a frame, wherein the frame comprising an upper fixing part 1 and a lower fixing part 5 which are separate or un-separate. The lower fixing part 5 can be provided by a back cover of the liquid crystal display device, and the upper fixing part 1 comprises a frame main body 11 and a sheet fixing rib 12. The sheet fixing rib 12 extends inwards from the frame main body 11 for pressing an edge of the top of a most upper sheet i.e. the protecting sheet 21 to fix the whole backlight module and protect the liquid crystal display device from damages of hitting or shaking directly.
Light properties of the frame comprising view angle of the whole monitor, light reflection and light efficiency influence effects of the backlight module a lot. Following are two ways of treating the light properties of the frame in this field:
(1) Using the black upper fixing part
The black upper fixing part 1 and white lower fixing part 5 are used.
Because the upper fixing part is black, emission light from the backlight module is sheltered. Furthermore, productions of the upper fixing part are easy. On the other hand, as a result of the whole upper fixing part 1 being black, light is absorbed thereby, which will reduce the light efficiency a lot. Besides, when users watch from lateral sides, shadow appears on the black upper fixing part, making the view angle smaller; thus, users have a illusion that the monitor is smaller.
(2) Using the white upper fixing part
Although replacing by the white upper fixing part can avoid the disadvantages of utilizing the black one, shinning lines appear instead as a result of reflecting light by white color. Thus, the sheets should be treated. Referring to FIG. 2, it shows printed regions of the sheet. Taking the sheet 21 as an example, a region of a top of the sheet 21 covered by the sheet fixing rib 211 should be printed with black ink when applying the white upper fixing part. The advantages of such backlight module are higher light efficiency, larger view angle and the liquid crystal display device seeming larger when users watching. On the other hand, the disadvantages are that printing ink onto the sheet is more difficult and costs of manufacturing is relative high.
Thus, it is necessary to provide a novel and improved frame to overcome the problems mentioned above.
One objective of the present invention is to provide a frame for use in a backlight module, wherein the backlight module comprising a light source, a light guiding plate, at least one sheet, wherein the sheet comprising a top and an edge, and the frame comprising an upper fixing part and a lower fixing part. The upper fixing part comprises a frame main body and a sheet fixing rib, wherein the sheet fixing rib with a light absorbing layer on the inner contacting surface extends inwards from the frame main body to press an edge of the top of the at least one sheet, and the light absorbing layer disposed on the inner contacting surface of the sheet fixing rib can be a layer printed with dark-colored ink, a layer coated with dark-colored ink, an anti-reflection treatment layer, or a dark-colored layer integrally formed with the sheet fixing rib. The present invention has advantages that the backlight module prevents light reflecting and has a large viewing angle.